4242 research outputs found
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Werkzeuge zur Unterstützung des Betriebs von Offhore-Windparks : Gesamtbericht
No full textZiel des Projektvorhabens KrOW! - Kosten- und risikogesteuerter Betrieb von Offshore-Windparks ist es, die Prozessorganisation der strategischen und operativen Betriebsführung von Offshore-Windparks durch Entscheidungsunterstützungen zu verbessern. Hierfür wurden verschiedene Werkzeuge zur Unterstützung des Betriebspersonals und der strategischen Ausrichtung des Betriebsführungskonzeptes entwickelt, die in Einzelberichten oder als Gesamtbericht abgerufen werden können
Re-evaluating the impact of institutional distance on the location choice and success of foreign Investors : comparing Chinese and Western investors in Africa
Get PDFThis dissertation seeks to add to our understanding how the internationalization process of Chinese firms relates to the internationalization process of Western firms. The focus of this project was on the assumed competitive advantage for Chinese firms in relatively high-risk host countries. In the first part of my study I use a conceptual framework presented by Child and Marinova (2014) to study the role of institutional distance for the location choice of Chinese and U.S. firms. Contrary to popular believe, I found that Chinese investments are not directed to countries with a low level of IM and investments from both China and the U.S. are directed to countries with a low level of political stability. In the second study I use process tracing to further study the causal mechanism that could explain how the levels of political stability and institutional maturity in China could give Chinese firms an advantage in high-risk emerging markets far away from China. The combination of the two studies shows that the success of Chinese firms in challenging host markets depends on much more than push factors only
Impacts of environmental changes on the global distribution of coral reefs
No full textCoral reefs support high biological diversity of marine life, and are highly productive ecosystems. Environmental perturbations exert profound influence on coral reefs. Elucidating environmental limits for coral growth and understanding the response of reef habitat suitability to environmental change are central to projecting future impacts of climate change on coral reef ecosystems and their biogeography under changing environmental conditions. I use the diagnostic model ReefHab in combination with most recent environmental variables to define the coral reef tolerance limits. By using the global data of coral reef occurrence as a proxy for their long-term adaptation to contextual environmental conditions, I calculate the reef habitat suitability functions. Then I explore the impact of global warming and ocean acidification on the potential reef habitat and habitat suitability in combination with ensemble data of IPCC AR5 climate models. I also explore the combined effects of pairwise combinations of environmental factors on coral reefs. This thesis contributes to knowledge on the tolerance limits for coral reefs and the parametric function of reef habitat suitability
Als ich auf die Welt kam, fiel ich auf ein Schlachtfeld... : Figur, Schauspiel und Perspektive des Kindes in 'Deutschland, bleiche Mutter' (Helma Sanders-Brahms, 1980)
Get PDFForce-displacement motions of a lubricated and dry tapering process of an AlMgSi1 alloy
Get PDFLubricants are commonly used in metal forming to reduce friction between work piece and forming tool, to protect semi-finished products and goods against corrosion and to reduce tool load. According to the aim of environment friendly production technologies it is strived to realize dry forming by the absence of lubricants. In this study tapering of aluminium rods of an AlMgSi1 alloy with a tungsten carbide forming die is investigated. The diameter is tapered from 9.25 mm to 9.00 mm. The tapering investigations were performed lubricated as well as dry. The lubricated forming investigations showed a mean maximum press force of 5.4 kN /- 1.5 kN. The dry tapering investigations of aluminium alloys were stopped after two samples, due to aluminium adhesion in the forming zone, which prohibited tapering of more samples. Dry tapering processes lead to adhesion of aluminium in the deformation zone very quickly by the use of a tungsten carbide forming die, which prevents the tapering of a high quantity of aluminium rods
Dynamics and transport of instabilities in magnetized quasi-Keplerian Taylor-Couette flows
Get PDFThe stability and transition to turbulence in canonical shear flows have since long been an outstanding scientific problem. One of the most exciting examples of shear flow is Keplerian motion of gas and dust in accretion disks. Although the Keplerian velocity profile is linearly stable, the presence of magnetic fields gives rise to the magnetorotational instability (MRI). MRI is considered one of the most powerful sources of turbulence in hydrodynamically stable quasi-Keplerian flows, however obtaining observational evidence of its operation is challenging. Although the linear stability of Keplerian flows with applied external magnetic fields has been studied for decades, the influence of the instability on the outward angular momentum transport, an inherent prerequisite for accretion to occur, is still far from understood. The aim of this thesis was to provide a better understanding of angular momentum transport and nonlinear properties of the MRI. Motivated by recent laboratory experiments, the MRI driven by an azimuthal magnetic field in an electrically conducting fluid sheared between two concentric rotating cylinders (Taylor--Couette flow) was explored. The instability was studied numerically with both linear stability analysis and fully resolved direct numerical simulations of the Navier--Stokes and induction equations. It was found that at low magnetic Prandtl numbers, as those in liquid metals, the laminar Couette flow becomes unstable to a wave rotating in the azimuthal direction and standing in the axial direction via a supercritical Hopf bifurcation. Subsequently, the flow features a catastrophic transition to spatio-temporal chaos which is mediated by a subcritical Hopf bifurcation. The results are in quantitative agreement with the PROMISE experiment and dramatically extend its realizable parameter range. Subsequently, the enhancement of angular momentum transport by turbulent stresses in the highly turbulent flow regimes was determined. One regime is dominated by magnetically triggered inertial waves, with transport mostly due to velocity fluctuations, and another by magnetocoriolis waves, where magnetic field fluctuations prevail. The magnetic Reynolds number defines the type of turbulence, with a crossover around the critical value of . The results give a comprehensive picture of transport enhancement by MRI spanning from low (as in liquid metals) to high (as in plasma) magnetic Prandtl numbers. In the latter case the existence of a finite-amplitude dynamo was demonstrated. This suggests that accretion disks can operate self-sustaining MHD-turbulence and thereby transport angular momentum efficiently without the need of considering imposed magnetic fields
X-ray fluorescence scanning of discrete samples - a new tool for the geochemical characterization of loess-paleosol sequences
Get PDFLoess-paleosol sequences (LPS) are among the most important terrestrial archives of paleoclimate for the Quaternary and provide valuable information about past environmental changes on millennial to multi-millennial time scales. Magnetic susceptibility and grain-size are proven as reliable proxies for pedogenesis and wind activity. Thus, to analyse these proxies, LPS are sampled in high spatial resolutions down to 2 cm. In contrast, geochemical data indicating weathering intensity, dust provenance and grain-size dynamics are often acquired with 10 cm resolution at best by using time- and cost-intensive quantitative analytical methods. However, results derived from X-ray fluorescence (XRF) scanning in the marine and lacustrine realm demonstrate that determining qualitative, relative changes in the elemental composition of a profile is generally sufficient to track paleoenvironmental changes at a high spatial resolution down to 100 micrometre. With the design of sample holders that allow measurements of discrete samples with an ITRAX XRF core-scanner, it becomes possible to exploit the unused potential of high-resolution samples previously taken for grain-size analysis as to geochemistry. Consequently, the aim of this study is to benchmark XRF scanning of discrete samples against other proxy data to evaluate the potential of high-resolution qualitative geochemistry unravelling weathering intensity, dust source changes and grain-size variations. For this purpose, three well-studied European LPS (Schwalbenberg II, Germany; Susak, Croatia; Süttö, Hungary) have been considered. They cover different time periods from Marine Isotope Stage (MIS) 7 to MIS 2 and are predominantly influenced either by oceanic, continental or Mediterranean climate respectively
Fragmentierung eines Service Ecosystem : eine Grounded-Theory-Studie zur Instandhaltung in der Windenergiebranche
Get PDFAn efficient operation management of wind turbines decisively depends on the design of the operational and strategic maintenance. The technical operator representing the owner of a wind energy plant and the technical service provider responsible for carrying out the maintenance were identified as the most relevant stakeholders. They are part of a service ecosystem, i. e. a spontaneously reacting structure of economically acting actors for the perception and answering of inner and outer stimuli. This study examines the symbolic collaboration between the technical operator and the technical service provider. The fragmentation of the service ecosystem is demonstrated by means of the grounded theory methode. The explanatory and predictive theory established in this context embeds the phenomenon of fragmentation of the service ecosystem into a cause and effect relationship around the two independent variables a standardizationa and a full service contractsa
The State-of-the-Art of Collaborative Technologies for Initial Vocational Education: A Systematic Literature Review
Get PDFFuture workplaces require collaboration skills in which members of different work communities use technologies to solve complex problems. Vocational education and training (VET) programs need to meet the challenge to prepare students to be part of a competent workforce. Particularly initial vocational education is under pressure to develop learners collaboration skills and abilities. To date, however, no attempt has been made to perform a comprehensive review of the use of computer-supported collaborative learning (CSCL) technologies across different vocational education settings to account for contextual factors of VET. In this systematic review, 26 published studies were analyzed with respect to their demographics, research methodology, use of technology, and measured outcomes. This review illuminates that research on CSCL still leaves the vocational learning context as an under-represented field of study. At the same time, technologies offer a range of new types of learning possibilities for vocational education. As the direct result of that development, vocational education is increasingly taking place in new technology-enhanced learning settings. Education can benefit from the opportunities of CSCL technologies, but on the other hand, such technologies create new challenges for facilitating vocational learning. Therefore, this review also identifies three topic areas specific to vocational learning (collaborative writing-to-learn, simulations and game-like solutions, and tangible objects) and enumerates desirable lines for future research
Vocational Teaching-Learning through the Eyes of Undergraduate Vocational Students in Malta: A Qualitative Exploratory Study
Get PDFThe purpose of this study is to develop a deeper understanding of the teaching qualities of effective lecturers that vocational students desire, students assessment preferences and preferred learning environments. This study gives a voice to higher vocational students as it is important for vocational educators to learn what attracts students to effective learning. Due to the inquiry s exploratory nature, an interpretivist approach was used, and a constructivist grounded approach using qualitative data was adopted. A purposive approach to multiple case study selection was used where the unit of analysis was a higher vocational student. The perceptions and expectations of vocational undergraduate (EQF level 6) students in two disciplines (applied science and engineering) were explored, to identify what may constitute good practice. A total of ten participants from two different institutes within the vocational university college agreed to be interviewed. Semi-structured and photo-elicitation interviews were applied. In addition, the Powerful Learning Environments (PLEs) Framework was used as a preliminary tool to aid in the decision-making process for data collection. Iterative analysis was used for the semi- structured interviews, whilst a constant-comparative method was used for the photo- elicitation image analysis. Overall, the expectations and preferences between both groups were very similar. Results show that students expect to be taught by interactive lectures that relate theory to practice that will prepare them for the job. Formal lectures including presentations were the least favoured. Regarding teaching qualities, students expect approachable and understanding lecturers who provide concrete industrial examples. Assessment preferences included home based assignments and research projects. The preferred learning environment is in line with most characteristics of the Powerful Learning Environment. Evidence shows that there is no particular difference between a higher vocational stu- dent and a higher education student. Implications for the enhancement of students learning processes are discussed and recommendations for further research are elaborated